Well, I will let McKnight say what is needed to be said. See the full entry of what McKnight is referring here. McKnight’s original post is here.

What we are seeing here is not so much a clash of theology, as a clash of methodology. The Reformed critics of Wright do their theology of penal substitution systematically. Wright does his historically/narratively. Unfortunately, Wright does not appreciate Pierced for our Transgressions for what it is (a marvelous systematic look at the doctrine of penal substitution). But neither do Wright’s critics appreciate Wright’s work for what it is (a marvelous grounding of this doctrine in historical context).